Many vehicles currently employ exhaust systems with decorative features in close proximity to the tailpipe and related components. Often these decorative features are curved and in close proximity to exhaust soot and condensate emanating from the tailpipe of vehicles during operation. The exhaust soot and/or condensate often deposits, discolors and otherwise adversely impacts these decorative features. Customer dissatisfaction is one adverse impact associated with these effects.
Vehicles with gasoline turbocharged direct injection (GTDI) engines are particularly prone to this problem. These engines produce high levels of carbon soot due to the level of enrichment required to maintain an acceptable throttle response under wide open throttle conditions. This soot exits the tailpipe as gas-borne and condensate-borne particulate. Both mechanisms of soot contribute to high rates of soot accumulation on the vehicle surfaces in close proximity to the tailpipe, particularly decorative exhaust tips and/or rear fascia. These soot accumulation rates are higher in vehicles with GDTI engines as compared to vehicles with non-GDTI engines.
Often the design of exhaust assemblies for a vehicle is driven in significant part by aesthetic considerations with various engineering constraints governed by the power systems and other aspects of the drive system selected for a given vehicle. Conventional methods of designing exhaust assemblies are iterative and rely on numerous computer aided design (CAD)-models that are tested using computational fluid dynamics (CFD) simulation models. Typically, these CAD models are developed on a time consuming element-by-element basis and then repeatedly tested through computer simulations. Considerations related to soot accumulation and discoloration are not understood through these conventional computer simulations. Often, only expensive prototype testing uncovers these problems late in the design cycle.
Accordingly, there is a need for exhaust assemblies that eliminate and/or mitigate the adverse effects associated with soot accumulation, discoloration and the like on the surfaces of a vehicle in proximity to the tailpipe. There is also a need for a more efficient model and approach to designing exhaust assemblies for vehicles in view of these adverse effects and other engineering considerations.